Monday's killings were the culmination of a bitter, years-long custody battle involving the slain woman and the gunman's son

DOVER, Del. — Authorities who uncovered a small arsenal kept by a onetime police officer who killed his former daughter-in-law and another woman at a Delaware courthouse said in a search warrant affidavit that investigators suspect the gunman's wife and son of helping to plot the slaying.

Monday's killings were the culmination of a bitter, years-long custody battle involving the slain woman and the gunman's son. The gunman, Thomas Matusiewicz, had previously complained that his family wasn't getting justice in a lawsuit she filed against them over the kidnapping of the pair's three daughters.

Matusiewicz (muh-TOO'-suh-wits) complained in an August 2011 letter to a Delaware judge that he and his family had no money to defend themselves in the lawsuit Christine Belford filed as her ex-husband David Matusiewicz awaited sentencing for taking the girls to Central America.

"We've lost or spent over a million dollars trying to get our grand-daughters to safety and now THERE IS NO MONEY LEFT AND THEY ARE STILL IN CUSTODY OF THEIR MOTHER (who has been in the care of someone in the mental health profession for over 20 years)!," Thomas and his wife, Lenore Matusiewicz, wrote in boldface letters.

"Is it true as they say, you only get the amount of justice you can afford?" they added. "Well, I guess we aren't going to be getting any."

Delaware State Police said Thomas Matusiewicz, 68, walked into the lobby of the New Castle County Courthouse in Wilmington on Monday and shot and killed Belford, 39, and her friend Laura Mulford, 47, before taking his own life.

According to an affidavit filed by Texas authorities to search Thomas Matusiewicz's home in Edcouch, Texas, he was carrying handwritten death certificates for Belford and Timothy Hitchings, an attorney representing her in the divorce and custody battle, when he entered the Delaware courthouse.

Texas authorities also said in the affidavit that Thomas Matusiewicz, his wife and his son were all suspected of "intentionally and knowingly participating in a murder."

Sgt. Paul Shavack, a spokesman for the Delaware State Police, had no immediate comment about the Texas affidavit naming David and Lenore Matusiewicz as suspects. He also declined to discuss details of papers found on Thomas Matusiewicz's body.

Law enforcement officials in Texas found eight guns found inside the Matusiewicz home and in a recreational vehicle on the property, and five more guns at a storage unit in Donna, Texas. Investigators said record checks on all the weapons came back clear. Thomas Matusiewicz once worked as a police officer in Vineland, N.J.

Authorities also seized several boxes and jars of ammunition, letters, court documents, Veterans Affairs documents for Thomas Matusiewicz, who served in the Navy, and a book entitled "Kill All the Lawyers."

Hitchings said in an email that he had no firsthand information about being targeted.

Neither David Matusiewicz nor his mother has been arrested in connection with the shooting, but David Matusiewicz is being detained by federal authorities who say he has violated the terms of his probation. Authorities allege in court documents that he failed to disclose that he spent the night before the shooting at a home in Elkton, Md., and that he has not paid restitution and child support as ordered.

"We will let you know when we are ready to speak as a family mourning for the loss of all victims in this tragedy," she said.

A tearful Lenore Matusiewicz told a Philadelphia TV news station on Wednesday that she had no idea of what her husband was planning.

"I wish I had known," she told WPVI-TV. "Maybe I could have done something to stop it."

"Our hearts go out to the other families, to those who were killed and to those who were wounded," she added.

She said, "I didn't want anybody dead."

Lenore Matusiewicz also said that she believes her husband's actions may have been affected by a brain tumor on the left side.

"It controls reasoning, memory, judgment, decision-making _ all of the higher functions. And it changed him," she told the news station.

The Delaware shooting was the culmination of years of acrimony in a bitter divorce and custody battle. At the heart of the dispute were the daughters of Belford and David Matusiewicz, now ages 7, 9 and 10.

David Matusiewicz pleaded guilty in 2009 to federal fraud and kidnapping charges after fleeing to Nicaragua in a motor home with his mother and the three girls.

David Matusiewicz, who was released from prison last year, kidnapped the girls after telling Belford they were going to Disney World for two weeks. The two were divorced and sharing custody at the time. Prosecutors say he forged his wife's signature to obtain nearly $250,000 from a Delaware bank, then sent the money to his parents' bank account and had his father transfer the money to a Bank of New Zealand account.

Belford sued her former husband, his parents and Gonzalez in 2009, claiming they worked together to carry out the kidnapping. She sought compensation for "medical, therapeutic, counseling, travel and other expenses."

Belford dropped the lawsuit in December 2011 after Thomas and Lenore Matusiewicz filed for bankruptcy protection in Texas.

"It became obvious that it was not going to be collectable," said Belford's attorney, James Woods. "I had no doubt she would win, and probably a very significant amount of money, for that torture they put her through."

Woods said the lawsuit was an attempt by Belford "just to try to get some justice."

"They had put her through hell, and it wasn't just David, it was certainly Lenore... and I found it incredibly hard to believe that Tom didn't know anything about it and participated in it, and Amy the sister as well."

Woods said that after Belford dropped the lawsuit, Thomas Matusiewicz sent him two thick packages of documents containing "all kinds of scandalous and ridiculous allegations" that Christine was abusing the children and was an unfit mother. The allegations were never substantiated, Belford was never charged and she was given full custody of the girls.

"It was obvious that there was so much venom they had directed toward Christine that it was almost palpable," Woods said.

Lenore Matusiewicz made similar allegations in a handwritten letter she addressed to Delaware Attorney General Beau Biden in January 2011. She was on probation at the time after serving more than a year in Delaware state prison for endangering the welfare of her three granddaughters related to the kidnapping.

She said her son was "paying the price for trying to protect his children...."

A federal judge who sentenced David Matusiewicz to prison noted that he never expressed any concern that his ex-wife was abusing their children until after he had been arrested.

A state judge who denied a motion by Lenore Matusiewicz to modify her prison sentence in 2010 also expressed skepticism about the abuse claims.

"Sadly, even if all the allegations of the defendant and her son are true, their decisions only seemed to harm the children more," the judge wrote.

Copyright 2013 Associated Press

Copyright 2015 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.